April 29, 2006

Y chromosome variation of Finns

An interesting comprehensive new article on Finnish Y-chromosome variation. The main finding is that the arrival of Finno-Ugric speakers (possessing haplogroup N3) was later followed by Scandinavian migrations mainly into western Finland, which reduced the frequency of N3 there, bringing especially haplogroup I1a. Thus, within Finland, western Finns are close to Swedes, and eastern Finns are close to their Finno-Ugric brethren. Interestingly, Finns seem to lack haplogroup R1b which is found among Germanic-speaking Scandinavians. Thus, the most probable sequence of events is the following:

1. Movement of N3 into Finland2. Movement of I1a into western Finland3. Movement of R1b into Germanic Scandinavia

This seems to support a picture in which early Germanics had a high frequency of I1a, early Finns had a high frequency of N3, and R1b in Scandinavia is the result of foreign settlers, probably continental Germans, Britons etc.

Twenty-two Y-chromosomal markers, consisting of fourteen biallelic markers (YAP/DYS287, M170, M253, P37, M223, 12f2, M9, P43, Tat, 92R7, P36, SRY-1532, M17, P25) and eight STRs (DYS19, DYS385a/b, DYS388, DYS389I/II, DYS390, DYS391, DYS392, DYS393), were analyzed in 536 unrelated Finnish males from eastern and western subpopulations of Finland. The aim of the study was to analyze regional differences in genetic variation within the country, and to analyze the population history of the Finns. Our results gave further support to the existence of a sharp genetic border between eastern and western Finns so far observed exclusively in Y-chromosomal variation. Both biallelic haplogroup and STR haplotype networks showed bifurcated structures, and similar clustering was evident in haplogroup and haplotype frequencies and genetic distances. These results suggest that the western and eastern parts of the country have been subject to partly different population histories, which is also supported by earlier archaeological, historical and genetic data. It seems probable that early migrations from Finno-Ugric sources affected the whole country, whereas subsequent migrations from Scandinavia had an impact mainly on the western parts of the country. The contacts between Finland and neighboring Finno-Ugric, Scandinavian and Baltic regions are evident. However, there is no support for recent migrations from Siberia and Central Europe. Our results emphasize the importance of incorporating Y-chromosomal data to reveal the population substructure which is often left undetected in mitochondrial DNA variation. Early assumptions of the homogeneity of the isolated Finnish population have now proven to be false, which may also have implications for future association studies.

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